In a glass plant molten glass is supplied to the glassware forming machines through a heated forehearth channel, and a feeder is provided at the downstream end of the forehearth channel in order to form gobs of glass for delivery to the various sections of a typical glassware forming machine. The feeder has a plurality of side-by-side vertically reciprocating refractory plungers and the lower end of each plunger is generally associated with an orifice defined in the lower portion of the feeder bowl into which the molten glass is received from the forehearth. An annular refractory tube surrounds the plungers and extends downwardly into the molten glass so that the bottom of the tube can cooperate with an annular seating surface inside the feeder bowl to interrupt the flow of glass when the feeder is to be shut down. During normal operation of the feeder this tube is raised to some predetermined height and rotates in the feeder bowl providing a passageway between its lower end and the feeder bowl through which the molten glass flows toward the orifices. The refractory tube is supported for rotation on its central axis in a frame which can be raised or lowered, and the frame is generally provided with means for rotating the refractory tube, which means includes an annular bevelled gear provided coaxially with the refractory tube. In a copending application entitled "Molten Glass Spout Bowl Refractory Tube Support Mechanism", Ser. No. 655,502, filed Sept. 27, 1984 now U.S. Pat. No. 4,554,000 such a mechanism is described in some detail. Another copending patent application Ser. No. 616,638 filed June 4, 1984 now U.S. Pat. No. 4,551,163 and entitled "Electronic Glass Feeder Plunger Operating Mechanism" describes in some detail the mechanism for operating the verticaly reciprocating refractory plungers. These two pending patent applications are incorporated by reference herein.
The present invention relates to an improved heat shield fitted to the upper end of the refractory tube, surrounding the vertically reciprocating plungers, and designed to reduce heat loss from the molten glass in the feeder bowl without interfering with vertical movement of the plungers, and rotating movement of the refractory tube.
Issued U.S. Pat. No. 4,328,023 shows a molten glass feeder having a refractory heat shield inside a refractory tube to reduce the exposed area above the molten glass in the feeder bowl and reduce heat loss. However, this prior art patent suggests a one-piece cast refractory shield which cannot be removed without first withdrawing the refractory plungers.
Issued U.S. Pat. No. 4,478,631 shows a molten glass feeder having heat baffles of refractory material provided inside a refractory tube to reduce the exposed area above the molten glass in the feeder bowl and avoid excessive heat loss. However, two unconnected heat baffles of cumbersome size are provided alongside the plungers in this prior art patent and because they are fabricated soley from refractory material these baffles must be designed to fit rather loosely inside the rotating refractory tube itself. The present invention represents an improvement over these prior art patents, and also provides advantages when utilized in a feeder of the type referred to in the above-identified pending patent applications. For example, both prior art configurations require different installations for different size refractory tubes. This requirement is obviated in the subject disclosure.